1. Field of the Invention
This invention relates to utility knives and, more particularly, concerns knives having a readily changeable and retractable blade.
2. Description of the Prior Art
Utility knives are known in the art. One such knife is disclosed in U.S. Pat. No. 4,227,306 in which a detachable blade is mounted between two handle halves or shells that form a handle and that are secured together by a screw. A disadvantage of this knife is that it is inconvenient and time consuming for a user to replace a used blade with a fresh blade since the handle halves must first be separated by detaching the screw. Another disadvantage of this knife is that the blade is not retractable leaving the blade exposed when the knife is not in use.
Utility knives having a retractable blade that is replaceable without taking the handle apart are also known in the art. For instance, U.S. Pat. No. 3,660,896 discloses a utility knife having a retractable blade that is carried by a blade carrier from a storage chamber, housing replacement blades, to an operable cutting position, and that is released from the handle by first moving the blade carrier laterally to disengage it from the blade and by then sliding the blade from the opening at the end of the handle. Knives of this type also are known that have magnetic loading means or adhesive loading means for securing a blade housed in the blade magazine to the blade carrier. However, these knives have the disadvantage of being complicated in their structure and operation.
Another utility knife is disclosed in U.S. Pat. No. 3,577,637 having a retractable blade that is replaceable without disassembling the handle. However, substituting a fresh blade for a used blade requires manipulating the blade carrier laterally to disengage the blade, sliding the blade from the opening at the front end of the handle and sliding a fresh blade into the opening. This utility knife has separate storage means for holding replacement blades.